Method of treating crude kraft soap



Feb.y 19, 1946. Y .1.J. LovAs ETAL y 2,395,233

METHOD OF TREATING CRUDE KRAFT SOAP Filed Aug. 1. 1942 ,VASTE V l 5 1 yy y 7711.

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Patented Feb. 19, 1946 UNITED STATES Plirlezla'rv oFFlCE Joseph JohnLovas, Ridgewood, and Paul F. Bruins, Douglaston, N. Y.

Application August 1, 1942, Serial No. 453,289

s clan'ns. (ci. 26o-97.5)

The present invention relates to an improved method of andmeans fortreating crude kraft pulp mill soap in order to separate out and recovertherefrom its component substances. Crude f kraft pulp mill soap isobtained from the waste black liquor of the soda and sulfate processesof pulping coniferous woods, and is made up of thel followingcomponents-sodium salts of fatty Type A--Hexane soluble rosin acid;

Type B-Hexane insoluble rosin acid;

Type C--Rosin acid, the sodium salt of which is soluble in hexane and inanhydrous acetone.

In addition to the above named sodium salts, the crude soap alsocontains oxidized rosin compounds and sterols.

In an application-filed by us of even date herecial operation, thisprocess could readily be converted, to continuous operation by acontinuous feed of dried soap and acetone. -The susbtantially anhydrousacetone acts as a solvent for the sterols and type C sodium resinate andsome of the type A and B sodium resinates. The action of the thickeneris to collect all of the acetone insoluble sodium salts of the fatty androsin acids as a sludge at the bottom, while acetone solution isdecanted. from the top as a clear solution. The sludge is piped from thebottom of the thickener to a mixing chamber 2, Where' hot water isadded. The hot water dissolves the sodium salts of the fatty and rosinacids and the oxidized rosin compound. The solution in chamber 2 is sentto a fractionating column or still 3 where acetone vapors are distilledoif, condensed in condenser I,

- and collected for re-use. v

with Ser. N0. 453,288, there is disclosed a method of and means forseparating the s odium salts of fatty acids and the sodium salts oftypes A and B rosin acids, from the oxidized rosin acids, sterols, andthe sodium salts of type C rosin acid, and then for separating each ofthe components from one another. Other procedures are also dis.

type C sodium resinate, ,and some sodium salts` of types A and B rosinacids, from the sodium salts of the fatty acids, the amount of types Aand B thus separated depending on the amount of water present, thenhydrolyzing the acid mixed After the acetone has been removed, the watersolution from still 3. is transferred to a hydrolyzing-tank 5 where amineral acid such as sulfuric acid is added to hydrolyze the sodiumsalts' v put in a still l where the hexane is distilled 01T,

salts into a mixed fattyand rosin acid, then sep.- l

from the types A and B sodium'resinates, separating the sterols from thetype C sodium resinate, and hydrolyzing and separating the type A rosinacid from the type B' rosin acid.

Referring to the annexed flow sheet diagram, we take ordinary crudekraft soap (usually containing betwcen 25% and 40% water) and spray dryit to reduce the water content thereof to within 0.5% to 5% water. Thedried material is conveyed into the top of a, Dorr thickener .|I, andpreferably .warm and substantially anhydrous acetone is fed into thebottom in the proportion of approximately 3-10 pounds of acetone to lpound oi dry material. For economical commercondensed in condenser 8Vand re-used, the free fatty and rosin acids come out as mixed acidswhich may be further worked or separated. As an alternative, the sludgemay be drawn off from the extractor, and the acetone stripped therefromto produce a soap containing chiefly sodium fatty acids, with a smallerportion of-sodlumfresinates and a still smaller portion of oxidizedrosin soap.

Such a final soap product can be utilized for blending for theproduction of certain grades of soaps, for example laundry soaps.

The acetone solution of the sterols and type Cy sodium resinate and someof the type, A and B sodium resinates, which was decanted from theadded. The hexane extracts sterols and type C sodium resinate from thesolution, while types A and B sodium resinates remain dissolved in thewater solution. On standing, the hexane solution forms a layer above thewater solution. The amount of type A and B resinates present in thewater solution will increase proportionately as the concentration ofwater in the original acetone or other ketone used is increased.

The top layer may be decanted off or the lower layer drained from thebottom, as may be preferred. The top layer is transferred to a still I3where the hexane is distilled off,A condensed, I 4, and recirculated.The remaining sterols and type C resinate are then placed in acrystallizer I5 where warm anhydrous acetone is added. The sterolscrystallize out on cooling while the type C resinate remains in solutionin the anhydrous acetone. The latter solution is then piped into a stillI8 where the anhydrous acetone is driven oil, condensed, I1, andrecirculated. The material remaining in the still I6 after thedistillation off of the acetone is type C sodium resinate, which isinsoluble in cold water but emulsifles in hot water. This type C sodiumresinate can be used "as is as a carrier for insecticide sprays since itisinsoluble in cold water and can be emulsified in hot water, or it maybe hydrolyzed to produce a very tacky (sticky) form of rosin acid, whichmay be valuable as an adhesive.

Returning to chamber I2, the lower layer comprising types A and B sodiumresinates in solution in water, is piped to a hydrolyzer 5', wheresulfuric acid and hexane are added. The acid hydrolyzes types A and Bresinates to their free acids. l'Ihe hexane is a solvent for type .Arosin acid but not for type B rosin acid. But type B rosin acid is alsoinsoluble in water so there are three layers formed in the hydrolyzer,the top one consisting of a hexane solution of type A `free rosin acid;a middle layer or suspension of type B rosin acid alone, and a bottomlayer comprising a water solution of sodium sulfate. 'I'he two upperlayers may be de canted oif and are placed in a vessel I9. The solutionof hexane containing type A rosin acid is then placed in a still 20where the hexane is distilled off, condensed, 2|, and recirculated.

Types A and B sodium resinates in solution in water may, if desirable,be concentrated to form a dark brown Asyrupy water solution of sodiumresinates suitable for use as a rosin size, for example, in sizingpapers such as kraft papers. If it is further desired, this concentratedsyrup of sodium reainates may be dried to a solid or powder form,

sbyspray drying.

The above procedure, therefore, results in recovering from the crudekraft soap, as end products of the process, white crystals ofsubstantially pure sterols, chiefly sit'osterols: a hydrocarbon solublesodium resinate (type C) a rosin acid (type A) which is soluble in hothexane and a rosin acid (type B) which is insoluble in hot hexane; fattyand rosin acids; and a small amount of hexane-insoluble oxidized rosin.

The fatty acids may be separated from the rosin acids by a process whichforms the subject matter of our above mentioned copending application.

It has heretofore been stated that the ordinary crude kraft soap may bedried to reduce the water content to upwards of 5% water. Likewise, the

ketone, of which acetone is our preferred form,l

may, contain some water. We prefer that the total or combinedwatercontent not exceed 10% of the whole, and it is always best that'theprocess be operated in the absence of any substantial amount of water inthe crude soap. When any substantial amount of water is present in thecrude kraft soap, when it is added to the Dorr thickener, then adissolving action will be had upon the sodium fatty acid soap, whereas,in our process, it is desired that said soap remain undissolved until itis passed to the mixing tank. Normally th'e operation will be conductedwith 97-100% ketone, and the range 95-100% ketone is included insubstantially anhydrous ketone."

Any ketones, in which water is soluble, or at least slightly soluble,may be employed in our process. In the examples, acetone and methylethyl ketone (maximum water solubility about 11% water) were specified,but in general, ketones with a structure containing up to 8 or 9 carbonatoms may be used and, as examples, we may mention di-ethyl ketone(slightly water soluble) and ethyl propyl ketone (very slightly Watersoluble). Water is generally insoluble in the higher ketones.

The mixture of fatty acids and rosin acids as produced and covered bythis method will contain between about 55% and 95% fatty acids andbetween about 5% and 45% rosin acids, the fatty acid content dependingupon the water present during the ketone extraction. For example,whenlusing anhydrous acetone having a ketone content of 99.5% and driedsoap having a moisture content'of about 2%,1the i'lnal mixed acid willbe found to analyze approximately 5560% fatty acid and about i5-40%rosin acids. As a further example, when using acetone with a ketonecontent of 97% by weight and a similar dried soap of 2% moisturecontent, the final mixed acid product will be found to analyzeapproximately -90% fatty acid content and about 20-l0% rosin acidcontent.

In general, the more water present, the higher will be the fatty acidcontent andthe lower the rosin acid content of the ilnal mixed acids.The mixed acid product recovered will be found to be clear and stableand have no offensive odor such as was originally present in theoriginal raw material used. The odor of the product will be similar tothat of oleic acid. The quality of this finished mixed acid product willalso be found to be very high since it will be substantially free fromunsaponiable matter, oxidized rosins and undesired sulfur compounds. The

-product is of such high grade that it may be readily adapted and usedfor direct hydrogenation for .the production of atearic acid and alsofor the production of acid estera by direct esteriiication. It ma 'beused directlyby saponication for'thcfl'olflitlnncf'hilh grade cold watersoluble arc'suitabe for use in the textile industry 'as well asinsynthetic rubber and synthetic'resin polymerization. The product mayalso be used directly for the production of vinyl esters of carboxylicacids for use in synthetic resin polymerizations. The particular fattyacids present in this mixed acid product are chiefly water-insoluble,unsaturated, fatty acids having 12 or more carbon atoms to the moleculehaving a molecular weight of at least 250 and a boiling point of atleast 200 C. at 50 mm. When using some types of crude kraft soap in themanner described, the final mixed acid product sometimes contains asmalll amount or traces of water-insoluble, saturated fatty acids havinga molecular weight of at least 250.

Having described our invention, what we claim and desire to secure byLetters Patent is follows: o

l. The process of treating a dried crude kraft soap which comprisesadding thereto substantially anhydrous liquid aliphatic ketone of notmore than 9 carbon atoms per molecule and therebydissolving sterols,other unsaponiilables, and also the ketone soluble sodium reslnates,

and removing thel undissolve'd sodium salts oi fatty and rosin acids andoxidized rosins.

2. The process vof treating -dried crude kraft soap which comprisesfeeding said dried-material to an extractor while feeding into thebottom of the extractor substantially anhydrous aliv phatic ketone oi'not more than 9 carbon atoms per molecule, collecting an overflowcontaining sterols, other unsaponiables, and the ketone soluble sodiumresinates, in ketone solution, and removing the undissolved sodium saltsof fatty I- and rosin acids and oxidized rosins.

3. The process` of treating dried crude krait soap which comprisesadding thereto substantially 'anhydrous aliphatic ketone of not morethan 9 carbon atoms per molecule, separating the thereby dissolvedportion from the undissolved portion, dissolving the latter in hotwater. re-

moving the ketone from the resulting solution. adding acid to thesolution in the presence of water to hydrolyze the sodium salts ofvfattyand rosin acids, adding hexane to take `up the free acids, andseparating out the materials not dissolved by the hydrocarbon, andremoving the and a water layer containing sodium resinates,

- separating the layers, treating the water layer hydrocarbon to recoverthe mixed free fatty and rosin acids. o t

4. A process of treating dried crude kraft ,soap which comprises addingthereto substantially anhydrous aliphaticl ketone of not more than 9carbon atoms per molecule, separating the di's solved portion from theundissolved portion, removing the ketone from the dissolved portion andadding water to the ketone-free solution, then adding hexane `and mixingthe same with the solution to form two layers, a hydrocarbon layer lthan9 carbon atoms per molecule and thereby dissolving the ketone-soluble;constituents of the soap, separating said' dissolved portion from theundissolved portion and adding water to the latter, stripping said watersolution oi? ketone, adding mineral acid to said water solution, wherebythe sodium fatty acid salts and rosin acid salts,

including oxidized rosin acid salts oi said solution are hydrolyzed totheir free acid components, adding a hexane `whereby the said acids arebrought into solution and the oxidized rosin is precipitated, separatingout the oxidized rosin,

and removing the solvent from the said acids.

l 8. A process, in accordance with claim 1, in which the ketonicsolution containing sterols. other unsaponiilables and sodium resinatesis substantially stripped of the ketone solvent, followed by the stepsof adding water to the ketone-free solution, then adding hexane andmixing the same with the solution to form two layers. a. hydrocarbonlayer and a water layer, separating the layers. stripping thehydrocarbon from its layer,

adding substantially anhydrous ketone to the said hydrocarbon-freedlayer, chilling said layer to crystallize out the sterols and strippingthe ketone from the remaining material to produce a residue consistingof sodium resinate. l

' vJOiEPH JOHN LOVAS. PAUL F. BRUINB.

